Spatial Distribution and Temporal Change of Water Volume and Quality of Throughfall and Stemflow

Abstract

Water volume and quality of throughfall and stemflow were examined for their spatial distribution and temporal change by observations under a single conifer tree on rainy days and by simulations using “tree crown water migration model”. Observation results showed that throughfall decreased on an average as the distance from stem decreased but some spots had more throughfall than rainfall, that reaching rate increased as the total of throughfall and stemflow increased, that acid rainfall was neutralized by tree crown, that stemflow had more solute than rainfall but stemflow was both less or more acid than rainfall, that throughfall was enriched with Cl-, N03-N, S04-S and NH4-N than rainfall, that the concentration of throughfall was higher near the stem than near the tree crown edge, and that the concentration of throughfall became low as time passed. Spatial distribution of throughfall was examined using the tree crown water migration model which represents the interception and migration within tree crown as those in and between boxes covering the profile of tree crown. Simulations using this model showed that both interception and migration to the direction of the tree crown edge accounted for the spatial distribution of throughfall.